mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2025-02-05 11:46:42 +00:00
29cc44c07b
hit from IR but creates a minefield for MI passes. The x86 backend has fairly powerful logic to try and fold loads that feed register operands to instructions into a memory operand on the instruction. This is almost always a good thing, but there are specific relocated loads that are only allowed to appear in specific instructions. Notably, R_X86_64_GOTTPOFF is only allowed in `movq` and `addq`. This patch blocks folding of memory operands using this relocation unless the target is in fact `addq`. The particular relocation indicates why we simply don't hit this under normal circumstances. This relocation is only used for TLS, and it gets used in very specific ways in conjunction with %fs-relative addressing. The result is that loads using this relocation are essentially never eligible for folding into an instruction's memory operands. Unless, of course, you have an MI pass that inserts usage of such a load. I have exactly such an MI pass and was greeted by truly mysterious miscompiles where the linker replaced my instruction with a completely garbage byte sequence. Go team. This is the only such relocation I'm aware of in x86, but there may be others that need to be similarly restricted. Fixes PR36165. Differential Revision: https://reviews.llvm.org/D42732 llvm-svn: 324546
Low Level Virtual Machine (LLVM) ================================ This directory and its subdirectories contain source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and runtime environments. LLVM is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt. Please see the documentation provided in docs/ for further assistance with LLVM, and in particular docs/GettingStarted.rst for getting started with LLVM and docs/README.txt for an overview of LLVM's documentation setup. If you are writing a package for LLVM, see docs/Packaging.rst for our suggestions.